<html>

<head>
  <title>设定各级标题</title>
</head>

<body>
  <h1 align="center">一级标题。</h1>
  <h2>二级标题。</h2>
  <h3>三级标题。</h3>
  <h4>四级标题。</h4>
  <h5 align="right">五级标题。</h5>
  <h6 align="left">六级标题。</h6>
</body>

</html>